1. Field of the Invention
This invention relates to man-made fibers and other molded objects prepared from synthetic polymers having durable antistatic properties.
2. Description of the Prior Art
Generally, antistatic synthetic fibers, in the form of continuous filament or spun yarns are obtained by first melt-spinning a linear fiber-forming synthetic polymer in combination with an antistatic agent. It has often been suggested that antistatic polymer fibers, such as polyamide fibers, can be produced by melt-spinning a mixture of the fiber-forming polymer with such antistatic agents as polyalkylene oxides or their reaction products. For instance, suitable tetrol compounds can be chain extended for use as antistatic additives as described in U.S. Pat. No. 2,979,528.
It is known from the teachings of U.S. Pat. No. 3,147,301 that organic polymers can be modified to impart a slightly ionic or hydrophilic character thereto and to improve the dyeability and antistatic properties of the polymer by the use of sulfo-organic esters of fumaric and maleic acids. Such esters contain the salt of a sulfonic acid. In U.S. Pat. No. 3,894,077 there is disclosed a nitrogen containing antistatic agent for a plastic comprising a compound of the formula ##STR1## wherein R.sub.1 is a hydroxyalkyl group of the formula ##STR2## in which R.sub.4 is an alkyl group having 6 to 16 carbon atoms, R.sub.2 is a lower alkyl group having 1 to 4 carbon atoms or hydroxyalkyl group of the same kind as R.sub.1, R.sub.3 is a lower alkyl group having 1 to 4 carbon atoms and m is an integer of 1 to 4. Partly because such antistatic agents for plastics are not polymeric, these compounds are not permanent and tend to be removed by exposure to washing or drycleaning solvents.
The antistatic agent compounds utilized as reactants herein are disclosed in U.S. Pat. No. 2,830,082. These compounds are N-(hydroxyalkyl) taurine compounds having the following structure: ##STR3## wherein R is a member of the group consisting of hydrogen and alkali metals, R' is a member of the group consisting of hydrogen, the methyl radical and hydroxyalkyl radicals containing from 2 to 4 carbon atoms. These compounds also lack permanence to washing and drycleaning of the antistatic effect when they are incorporated in a textile fabric. Because they are derived from taurines these compounds are more expensive to prepare than many other antistatic agents presently existing in the prior art.
In German Pat. No. 2,318,308 there is disclosed an antistatic agent for polyamide fibers which is a polyoxyalkylated amino acid. These compositions can contain monovalent groups of the formula: ##STR4## in which X and Y are oxyalkylene units, R is an aliphatic, aromatic or cycloaliphatic group, Z is --COO-- residue, --SO.sub.2 O-- residue or a metal salt, x is 1 to 1,500 and y is 0 to 1,500. These materials attempt to combine the increased conductivity of polyoxyalkylated compounds with the polarizing effects of amine, carboxylate, sulfonate or other salt groups. While these materials can be of high molecular weight, such materials differ from the antistatic agent polyester compositions of the invention which contain repeating amino and sulfonate salt groupings along the polymer chain, thus making it possible to incorporate a greater proportion of amino and sulfonate groups in the molecular structure and obtain the advantages attendant thereon.
Generally, antistatic agents are incorporated in plastic materials, especially fibers, by processes which either involve impregnating the synthetic polymer fiber, for instance, a polyamide fiber subsequent to its being woven into a fabric or alternately by incorporating the antistatic agent into the polymer melt prior to spinning into filaments. Fibers extruded from such a melt are believed to contain the additive as an insoluble phase in the form of fine fibrils aligned with and dispersed throughout the fiber. Desirable fiber properties are generally not altered by the use of minor amounts of such additives, however, a substantial reduction in their tendency to acquire a static charge can result by the incorporation of an antistatic agent therein.